Uptake of nitrogen forms in higher plants: Molecular and physiological study of urea transport in Zea mays

Supervisor: Roberto Pinton

It is well known that organic nitrogen forms (such as peptides, amino acids and urea) are able to sustain plant growth but the quantitative contribution of these sources to overall nitrogen (N) nutrition of plants is still under debate. 
In the last decades agricultural N-fertilization has led to a tremendous urea input into biosphere, accounting for over 50% of the world N-fertilizer consumption1, especially due to its low cost production and its high nitrogen content. Therefore urea, nitrate and ammonium are the three forms of N generally used in cultivated soils. 
This research concerns physiological and molecular study of urea uptake in Zea mays in order to understand the contribution of different N sources and, particularly, to identify and characterize the high-affinity urea transporter DUR3. 
Concerning the first part of the project, maize plantlets were exposed to organic and inorganic N-sources and the urea uptake was analysed at different times of treatment using a spettrophotometric assay. The data showed that plantlets respond in a different way when the sources are supplied alone or in combination with other ones (e.g. urea in comparison to urea+nitrate). To understand if this physiological response was correlated to changes in transcriptomic profiles, roots of treated plantlets were subjected to microarray analyses performed using the NimbleGen technologies. 
Focusing on genes involved in the transport of N sources and in their assimilation, the time-course of expression levels was followed by using real time RT-PCR. Aim of the project is to characterize the putative high affinity urea transporter gene ZmDUR3 in maize, isolating the sequence and performing complementation assay in yeast. 
The identification and characterization of urea transporters in higher plants is important not only for understanding the urea-related plant N-nutrition processes, but also for exploring potential strategies to improve urea-based N-fertilizer use efficiency in agricultural crop production.

Fundings : This research programme has been financed within a research project by the Friuli Venezia Giulia Region (regional law n. 26/05 art.17-NORGEF-, Italy) entitled “Efficienza d’uso dell’azoto di origine organica in aree vulnerabili del Friuli Venezia Giulia: aspetti fisiologici, agronomici e ambientali” (scientific leader of research unit 2 prof. Roberto Pinton). Further support comes from a grant from Italian MIUR-PRIN 2011/13: “Sulphur use efficiency: acquisition mechanisms, rhizospheric processes and interactions with other nutrients” (prof. Roberto Pinton National Coordinator).

Biography and contacts
Laura Zanin was born in 1985 in Italy, 2009 graduated with honours (110/110) in Agricultural Biotechnology at Udine University (Italy). In 2010 she started the doctoral course at the PhD school “Agriculture Science and Biotechnology” at the University of Udine in collaboration with the “Centre of Functional Genomic of Plants” and the ”Institute of Plant Sciences” at the University of Bern where she performed the period of study abroad.

laura.zanin@uniud.it